A buckle device is one of critical structures of a helmet. Especially, when the wearer's helmet is hit because of an accident, the buckle device may loosen and fall due to an instantaneous impact force. Sometimes, the wearer's neck is cut by the locking component of the buckle device to endanger life. Therefore, if the buckle device cannot be buckled tightly or cannot avoid loosening when the helmet is hit, wearing a helmet has lost its significance. In addition to the need to buckle the buckle device tightly and to prevent loosening, whether the belt and the buckle structure can be operated with ease also affects the wearer's willingness to use the helmet. Especially in the cold winter, many people will wear gloves when riding a motorcycle to keep warm. When the rider arrives at the destination, he/she must first remove the gloves to hold the belt with one hand and to unbuckle the buckle device with the other hand. It is inconvenient for use.
In order to improve the above-mentioned deficiencies, please refer to WO 2015/056545, which discloses a buckle. A main shaft between two side plates of a housing is pivotally connected with a press member. A secondary shaft at the front end of the housing is pivotally connected with an operation lever. A main spring and a secondary spring are fitted on the main shaft and the secondary shaft, respectively. Wherein, a housing base, the press member and the operation lever can be folded into a Z-shape. The press member can be driven to turn by pulling the operation lever to disengage the press member from the housing base so that the buckle can be operated with one hand.
In addition, referring to WO 2010/117147, there is disclosed a buckle device for length adjustment. Two ends of a base unit are provided with a locking unit and a lever unit, respectively. The respective other ends of the locking unit and the lever unit, not connected with the base unit, are interconnected crosswise. When a belt unit having a plurality of saw teeth is inserted in the base unit, the lever unit can be rotated by pulling the lever unit with one hand to disengage the locking unit from the saw teeth of the belt unit.